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Functional plasticity in the type IV secretion system of Helicobacter pylori.

Barrozo RM, Cooke CL, Hansen LM, Lam AM, Gaddy JA, Johnson EM, Cariaga TA, Suarez G, Peek RM, Cover TL, Solnick JV - PLoS Pathog. (2013)

Bottom Line: CagY is an essential component of the H. pylori T4SS that has an unusual sequence structure, in which an extraordinary number of direct DNA repeats is predicted to cause rearrangements that invariably yield in-frame insertions or deletions.Here we demonstrate in murine and non-human primate models that immune-driven host selection of rearrangements in CagY is sufficient to cause gain or loss of function in the H. pylori T4SS.We propose that CagY functions as a sort of molecular switch or perhaps a rheostat that alters the function of the T4SS and "tunes" the host inflammatory response so as to maximize persistent infection.

View Article: PubMed Central - PubMed

Affiliation: Center for Comparative Medicine, University of California Davis, Davis, California, United States of America.

ABSTRACT
Helicobacter pylori causes clinical disease primarily in those individuals infected with a strain that carries the cytotoxin associated gene pathogenicity island (cagPAI). The cagPAI encodes a type IV secretion system (T4SS) that injects the CagA oncoprotein into epithelial cells and is required for induction of the pro-inflammatory cytokine, interleukin-8 (IL-8). CagY is an essential component of the H. pylori T4SS that has an unusual sequence structure, in which an extraordinary number of direct DNA repeats is predicted to cause rearrangements that invariably yield in-frame insertions or deletions. Here we demonstrate in murine and non-human primate models that immune-driven host selection of rearrangements in CagY is sufficient to cause gain or loss of function in the H. pylori T4SS. We propose that CagY functions as a sort of molecular switch or perhaps a rheostat that alters the function of the T4SS and "tunes" the host inflammatory response so as to maximize persistent infection.

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Recombination of cagY during infection of rhesus macaques and mice can also restore the capacity to induce IL-8.Rhesus macaques and mice were inoculated with mOut2, which does not induce IL-8 or translocate CagA. Single colony isolates were recovered and tested for induction of IL-8 and compared to mOut2 by cagY PCR-RFLP. (A) Colonies from three monkeys (36001, 35951, 35930) showed significantly increased capacity to induce IL-8 at 8 weeks compared to 2 weeks PI, which was associated with changes in cagY RFLP. The fourth monkey (36018) was colonized with a mixture of cagY genotypes that induced low IL-8 similar to mOut2. (B) Colonies recovered from WT and RAG2−/− mice typically induced low IL-8 similar to input mOut2, with no change in cagY. *P<0.05; ***P<0.001.
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ppat-1003189-g010: Recombination of cagY during infection of rhesus macaques and mice can also restore the capacity to induce IL-8.Rhesus macaques and mice were inoculated with mOut2, which does not induce IL-8 or translocate CagA. Single colony isolates were recovered and tested for induction of IL-8 and compared to mOut2 by cagY PCR-RFLP. (A) Colonies from three monkeys (36001, 35951, 35930) showed significantly increased capacity to induce IL-8 at 8 weeks compared to 2 weeks PI, which was associated with changes in cagY RFLP. The fourth monkey (36018) was colonized with a mixture of cagY genotypes that induced low IL-8 similar to mOut2. (B) Colonies recovered from WT and RAG2−/− mice typically induced low IL-8 similar to input mOut2, with no change in cagY. *P<0.05; ***P<0.001.

Mentions: Recombination in cagY could be a mechanism by which H. pylori modulates rather than evades the host inflammatory response. If so, in vivo cagY recombination might sometimes confer an increase in the function of the T4SS, and enhance rather than reduce H. pylori inflammatory potential. To address this hypothesis, we undertook experiments to investigate possible alterations in cagY that might occur if animals were challenged with H. pylori mOut2, which had undergone cagY recombination that eliminated function of the T4SS (Figure 4). As a first step, to exclude the possibility that additional mutations could have occurred in mOut2 that conferred loss of T4SS function, we used contraselection to replace the cagY in mOut2 with that from WT J166. The results demonstrated that replacement of cagY in this strain with cagY from WT J166 was sufficient to restore induction of IL-8 in mOut2 (Figure S6). In three of four monkeys infected with mOut2 (36001, 35951, 35930), most colonies recovered two weeks after challenge resembled the input, with low IL-8 induction and the same cagY PCR-RFLP (Figure 10A). However, by eight weeks there was a significant increase in the capacity to induce IL-8 that was accompanied by changes in the cagY RFLP. One of these three monkeys (36001) was sampled repeatedly up to 24 weeks post inoculation; all output colonies recovered 8 weeks or more PI induced IL-8 and expressed a cagY that differed from that in mOut2 (Figure S7). A fourth monkey (36018) was colonized with a mixed population of cagY variants, but nearly all induced low IL-8 similar to that of the challenge strain. We next infected C57BL/6 WT and RAG2−/− mice with mOut2, and analyzed IL-8 induction and cagY RFLP up to 16 weeks PI. Similar to infection with WT J166, colonization density of mOut2 was greater in RAG2−/− mice than in C57BL/6 mice (Figure S5B). In general, strains recovered from both WT and RAG2−/− mice induced low IL-8 similar to the input mOut2, with no change in cagY (Figure 10B). A few colonies from both WT and RAG2−/− mice showed increased IL-8, which was accompanied by a change in cagY. Strains from mice and monkeys that recovered IL-8 induction showed novel cagY RFLP fingerprints that did not revert to WT J166. These results demonstrate that in vivo recombination in cagY can either eliminate or restore the function of the T4SS encoded on the H. pylori cagPAI. Since CagY that confers a non-functional T4SS appears stable in mice, modulation may be driven more by inflammation rather than adaptive immune responses.


Functional plasticity in the type IV secretion system of Helicobacter pylori.

Barrozo RM, Cooke CL, Hansen LM, Lam AM, Gaddy JA, Johnson EM, Cariaga TA, Suarez G, Peek RM, Cover TL, Solnick JV - PLoS Pathog. (2013)

Recombination of cagY during infection of rhesus macaques and mice can also restore the capacity to induce IL-8.Rhesus macaques and mice were inoculated with mOut2, which does not induce IL-8 or translocate CagA. Single colony isolates were recovered and tested for induction of IL-8 and compared to mOut2 by cagY PCR-RFLP. (A) Colonies from three monkeys (36001, 35951, 35930) showed significantly increased capacity to induce IL-8 at 8 weeks compared to 2 weeks PI, which was associated with changes in cagY RFLP. The fourth monkey (36018) was colonized with a mixture of cagY genotypes that induced low IL-8 similar to mOut2. (B) Colonies recovered from WT and RAG2−/− mice typically induced low IL-8 similar to input mOut2, with no change in cagY. *P<0.05; ***P<0.001.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3585145&req=5

ppat-1003189-g010: Recombination of cagY during infection of rhesus macaques and mice can also restore the capacity to induce IL-8.Rhesus macaques and mice were inoculated with mOut2, which does not induce IL-8 or translocate CagA. Single colony isolates were recovered and tested for induction of IL-8 and compared to mOut2 by cagY PCR-RFLP. (A) Colonies from three monkeys (36001, 35951, 35930) showed significantly increased capacity to induce IL-8 at 8 weeks compared to 2 weeks PI, which was associated with changes in cagY RFLP. The fourth monkey (36018) was colonized with a mixture of cagY genotypes that induced low IL-8 similar to mOut2. (B) Colonies recovered from WT and RAG2−/− mice typically induced low IL-8 similar to input mOut2, with no change in cagY. *P<0.05; ***P<0.001.
Mentions: Recombination in cagY could be a mechanism by which H. pylori modulates rather than evades the host inflammatory response. If so, in vivo cagY recombination might sometimes confer an increase in the function of the T4SS, and enhance rather than reduce H. pylori inflammatory potential. To address this hypothesis, we undertook experiments to investigate possible alterations in cagY that might occur if animals were challenged with H. pylori mOut2, which had undergone cagY recombination that eliminated function of the T4SS (Figure 4). As a first step, to exclude the possibility that additional mutations could have occurred in mOut2 that conferred loss of T4SS function, we used contraselection to replace the cagY in mOut2 with that from WT J166. The results demonstrated that replacement of cagY in this strain with cagY from WT J166 was sufficient to restore induction of IL-8 in mOut2 (Figure S6). In three of four monkeys infected with mOut2 (36001, 35951, 35930), most colonies recovered two weeks after challenge resembled the input, with low IL-8 induction and the same cagY PCR-RFLP (Figure 10A). However, by eight weeks there was a significant increase in the capacity to induce IL-8 that was accompanied by changes in the cagY RFLP. One of these three monkeys (36001) was sampled repeatedly up to 24 weeks post inoculation; all output colonies recovered 8 weeks or more PI induced IL-8 and expressed a cagY that differed from that in mOut2 (Figure S7). A fourth monkey (36018) was colonized with a mixed population of cagY variants, but nearly all induced low IL-8 similar to that of the challenge strain. We next infected C57BL/6 WT and RAG2−/− mice with mOut2, and analyzed IL-8 induction and cagY RFLP up to 16 weeks PI. Similar to infection with WT J166, colonization density of mOut2 was greater in RAG2−/− mice than in C57BL/6 mice (Figure S5B). In general, strains recovered from both WT and RAG2−/− mice induced low IL-8 similar to the input mOut2, with no change in cagY (Figure 10B). A few colonies from both WT and RAG2−/− mice showed increased IL-8, which was accompanied by a change in cagY. Strains from mice and monkeys that recovered IL-8 induction showed novel cagY RFLP fingerprints that did not revert to WT J166. These results demonstrate that in vivo recombination in cagY can either eliminate or restore the function of the T4SS encoded on the H. pylori cagPAI. Since CagY that confers a non-functional T4SS appears stable in mice, modulation may be driven more by inflammation rather than adaptive immune responses.

Bottom Line: CagY is an essential component of the H. pylori T4SS that has an unusual sequence structure, in which an extraordinary number of direct DNA repeats is predicted to cause rearrangements that invariably yield in-frame insertions or deletions.Here we demonstrate in murine and non-human primate models that immune-driven host selection of rearrangements in CagY is sufficient to cause gain or loss of function in the H. pylori T4SS.We propose that CagY functions as a sort of molecular switch or perhaps a rheostat that alters the function of the T4SS and "tunes" the host inflammatory response so as to maximize persistent infection.

View Article: PubMed Central - PubMed

Affiliation: Center for Comparative Medicine, University of California Davis, Davis, California, United States of America.

ABSTRACT
Helicobacter pylori causes clinical disease primarily in those individuals infected with a strain that carries the cytotoxin associated gene pathogenicity island (cagPAI). The cagPAI encodes a type IV secretion system (T4SS) that injects the CagA oncoprotein into epithelial cells and is required for induction of the pro-inflammatory cytokine, interleukin-8 (IL-8). CagY is an essential component of the H. pylori T4SS that has an unusual sequence structure, in which an extraordinary number of direct DNA repeats is predicted to cause rearrangements that invariably yield in-frame insertions or deletions. Here we demonstrate in murine and non-human primate models that immune-driven host selection of rearrangements in CagY is sufficient to cause gain or loss of function in the H. pylori T4SS. We propose that CagY functions as a sort of molecular switch or perhaps a rheostat that alters the function of the T4SS and "tunes" the host inflammatory response so as to maximize persistent infection.

Show MeSH
Related in: MedlinePlus